Balanced high frequency circuit



S p 1941- A. M. BRAATEN 2,254,590

BALANCED HIGH FREQUENCY CIRCUIT Filed March 27, 1940 ZSheets-Sheet 1 0 4 oI/rPuT INV EN TOR. ARTHUR M. BRAAT'EN ATTORNEY;

p 1941- A. M. BRAATEN 1 2,254,590

BALANCED HIGH FREQUENCY CIRCUIT I Filed March 27, 1940 2 SheetS -Sheet 2 OUTPUT ourpur OUTPUT INVEN TOR. ARTHUR lvl. BRAATEN :BY r

ATTORNEY.

Patented Sept. 2, 1941 BALANCED HIGH FREQUENCY CIRCUIT Arthur M. Braaten, Riverhead, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application March 27, 194.0, SerialNo. 326,189

11 Claims. (Cl. 25036) This invention relates to a new and novel balanced high frequency condenser and circuit arrangement.

An object of this invention is to provide an efficient, balanced high frequency circuit in which the condenser and other circuit elements are arranged symmetrically with respect to ground.

Another object of thisinvention is to p-rovide a combined variable condenser and inductive system which is symmetrically arranged with respect to ground, and to give an eiiicient circuit arrangement for the ultra high frequencies.

A feature of this invention is the circuit arrangement of two metallic containers which serve as circuit terminals, both containers being arranged parallel to ground but insulated therefrom and located in the same horizontal plane but spaced apart in the vertical plane and electrically connected together in a new and novel circuit arrangement.

In many types of high frequency circuits, such as for example, oscillators, or measuring circuits, it'is often necessary that the circuits be perfectly balanced with respect to ground. At very high frequencies, it is practically impossible to obtain such a balance with ordinaryty'pes of coils and condensers, due to the difl'iculty of making the various parts of the circuit perfectly symmetrical with respect to ground. In the present system, a circuit can be easily made to obtain the desired condition of perfect'balance.

The circuit arrangement of this invention is not to be confused with the ordinary neutralizing circuit in which inductive units are symmetrically arranged and electrically connected together with respect to. a commonground terminal.

This invention will best be understood by referring to the. accompanying drawings, in which:

Fig. l is a plan view of the two metallic containers; 3

Fig. 2 is aphantomelevation viewcf Fig. 1;.

Fig. 3 is a diagrammatic circuit arrangement .of'

. -Fig. l6 is another. embodiment of this'invention in which both containers are provided with static trolled oscillation generator employing the balanced output coupling means shown in Fig. 6.

.Referring now in detail to the drawingaFigs. 1 and2 show two outwardly identicalcylinders, I

and 2,.which are made of conducting material and Y are, hollow. Inside of .l is avariable condensen, one side of which, 3, is connected to the cylinder electrically, while the other side, l, is insulated from the cylinder by the insulator 5. The insu- ,-;lator 5 which supports the condenser isfastened to theend of the cylinder by meansof the spacers t and screws 1. The variable plates of the con-V.

denser, connected to 3, are adjustable through a small hole 6a.

denser, and to thecylinder 2 at b. The wire 8. is

insulated from cylinder I, at a, by means of a, bushing (not shown). The two containers I and H-2 are not connected toground, as this would short-circuit the condenser. They are therefore insulated by'insulation material M and. placed in a symmetrical relationship with respectto ground, toequalize the capacities thereto. V

The manner in which. the condenser is usually used is as follows. The two-cylinders, being connested, oopposite sides of the .variablecondenser,

are themselves the terminals of the completecondenser system. .Since they are alike physically,

they have equal capacities to ground, assuming of course that they are situated symmetrically,

with respect to ground. However, since wire 8 is connected to one, cylinder .and not to the other, the balance to grounclcannot be perfect. To corE -rectthis unbalance, a second wire 9, of the same.

size as 3, is connectedto cylinder l, at c, and is run .parallel .to 8. .At d, it passes through an insulated hole, on.into the interior 013,2. It is, evident that the. two sides ,of the condenser are now perfectly symmetrical with respect to ground,

assuming the ground to be perpendicular to the axes ofsthe cylinders.

Fig. 3 shows how the addition of an inductance within the empty cylinder creates a tuned circuit whichis perfectly balanced to ground. One side of L1 is connected to'the wall of the cylinder; the

opposite end connects to the end of the wire 9; thus, the coil is in parallel with the condenser;

The tuned circuit may be connected to a balanced Cylinder 2 is empty. A wire 8,. passing, through ahole at a, isconnected to the. stationary or fixed side 4, of the variable con-.

3| is connected at the center ground connection to cathodes 24. A resistance 33 is connected between the cathode and grid of each discharge device.

Here, the cylinders are divided into two compartments each by static shields S and S1. The variable condenser is placed in one compartment and the tuning coil in the corresponding compartment of the other cylinder. On the opposite sides of the electrostatic shields which divide the interiors of the cylinders are located two identical inductances La and L3. These are symmetrically located in 'their respective compartments, so that they will each have the same capacity to the cylinders. The leads to the coils pass through] two tubes, g and h, which are symmetrically located on the cylinders. The coils L2 and Le may be connected either in series or in parallel, at the center point P. 1 Y

Coil L2 is magnetically coupled to L1. L3 is a dummy coil which merely balances the capacity which L2 has to its container Since L2 cannot be moved without. destroying the balances between L2 and L3 and their respective containers, the coupling can be' varied by means of L1.

If the system of Fig. 6 is. symmetrically ar-' ranged with respectto ground and is connected at symmetrically located points e and f to any balanced networlg'as, for instance, a balanced oscillator'or' measuring circuit, the system will be perfectly balanced to ground. It should be understood that wires 8 and 9 are actually located. in a plane parallel to ground as shown by Figs. 1 and 2. They are shown one above the other in the circuit diagrams merely for the sake of convenience.

Circuits similar to those shown may be used at allfrequencies. but will be found especially useful at very highfrequencies, where stray capacitance is so important a factor.

InFiQ. 7.15 shown one of the possible ways in V which the present invention may be used. Here itis connectedin the plate circuit of a balanced.

1 line-controlled oscillation generator, where it provides a balanced output coupling means at P; The circuit arrangement of Fig. '7 comprises two electron discharge devices 20 and 2| each having anodes 22, grids 23 and cathodes 24. The.

container l is connected to plate 22 of the electron discharge device 20 through the fixed cou pling condenser 25. The general arrangement of the connections between containers I. and 2 is similar to that of Fig. 6. 7 Electron discharge device 2! is connected to container 2 through'a fixed cond'enser 2B interposed between container 2 and the anode 2 2. A pair of chokes 21 and 28 are symmetrically arranged between anodes 22 and a source of plate supply voltage B. A symmetrically arranged concentric conductor having a =length of one-quarter wave-length arranged each side of ground comprises an inner cylindrical conductor 30 and an outer cylindrical conductor .3l. The inner, conductor 30 is coupled to grids 23 by means of fixed coupling condensers 32. Theconnection points on 30 are symmetri-- Although only a few embodiments of this invention have been discussed, it is to be distinctly understood that it should not be limited precisely thereto.

.What is claimed is:

1. A high frequency balanced circuit comprising a first and a second metallic container sy metrically arranged adjacent each other and 'having equal capacity to ground, each container serving as one terminal for said circuit, a fixed and a variable plate element located within said first container, one of said plate elements insulatingly supported from said first container, the other plate element connected to said first container, and an electrical connection from the insulatingly supported plate element to said second container. 7

2. A high frequency balanced circuit comprising a first and a second metallic container arranged symmetrically and each having equal capacity to ground, said'containers located adjacent each other and insulated from ground, each container serving as one terminal for said cir-' cuit, a fixed and a variable plate element located within said first container, one of said plate elements insulatingly supported from said first container, the other plate element connected to said first container, and an electrical connection from' the insulatingly supported plate element to said second container.

3. A high frequency balanced circuit comprising a first and a second metallic container symmetrically arranged adjacent each other and having equal capacity to ground, each container serving as one terminal for said circuit, a fixed and a variable plate element located within said first container, one of said plate elements insulatingly supported from said first container, the other plate element connected to said first container, and an electrical connection comprising two leads forming an electrical connection symmetrically arranged, one of said leads connected to said second container and to the plate element which is insulatingly supported, the other lead connected to said first container and passing through the wall of said second container but insulated therefrom.

irrespective of the position of the plate elements of saidvariable condenser.

5. A high frequency balanced condenser circuitincluding a first and a second metallic container, 'each container symmetrically located with respect toground and having equal capacity thereto, an inductance unit within said second container, a variable condenser within said first container, and circuit coupling means between said containers whereby a balanced circuit is obtained irrespective of the position of the plate said containers being symmetrically located with respect to ground and having equal capacity thereto, a pair of inductance units in coupled relationship with each other and located within said second container, a variable condenser within said first container, and circuit coupling means between said containers whereby a balanced circuit is obtained irrespective of the position of the plate elements of said variable condenser.

7. A high frequency balanced condenser circult including a first and a second metallic container, each container symmetrically to have equal capacity to ground and located in the same horizontal plane but spaced apart from each other in the vertical plane, a pair of inductance units in coupled relationship to each other, an electrostatic shield interposed between said inductance units, said inductances and said electrostatic shield located within said second container, a variable condenser within said first container, and circuit coupling means between said containers whereby a balanced circuit is obtained irrespective of the position of the plate elements of said variable condenser.

8. A high frequency balanced condenser circuit including a first and a second metallic container, said containers symmetrically located with respect to each other and to have equal capacity to ground, a variable condenser and an inductance coil within said first container, and an electrostatic shield interposed between said condenser and said inductance coil, a pair of inductance coils in coupled relationship to each other and located within said second container, an electrostatic shield interposed between said inductance coils, and circuit coupling means between said containers whereby a balanced circuit is obtained irrespective of the position of the plates of said variable condenser.

9. A high frequency line-controlled oscillation generator circuit comprising a pair of electron discharge tubes symmetrically arranged and coupled to a first and second metallic container symmetrically arranged adjacent each other and having equal capacity to ground, a fixed and a variable plate element located within said first container, a pair of inductance coils in coupled relationship to each other and located within said second container, and a pair of output leads for said oscillator connected to at least one of the inductance coils located within each of the containers.

10. A high frequency balanced oscillation generator circuit comprising a pair of electron discharge tubes coupled to a first and second metallic container symmetrically arranged and having equal capacity to ground, said discharge tubes and containers being arranged in balanced relation with respect to ground, a variable capacitor and an inductance located within said first container, a pair of inductances in coupled relationship located within said second container, a tuned circuit comprising the said variable capacitor in the first container and an inductance within the second container so connected to maintain a balanced relation between containers and ground, and a coupling circuit consisting of an inductance in each container connected so as to give a balanced output.

11. A high frequency oscillation generator comprising a pair of electron discharge devices, two metallic containers symmetrically arranged and having equal capacity to ground, the first containing a variable capacitor and an inductance, the second a pair of inductances in coupled relationship, a tuned circuit consisting of the variable capacitor in the first container and an inductance in the second container, a coupling circuit consisting of an inductance in each of said containers, said discharge devices,

containers, tuned circuit and coupling circuit so connected and disposed to effect a circuit balanced with respect to ground.

ARTHUR M. BBAATEN. 

